1. Field of the Invention
This invention relates to the field of laboratory dryers such as those used to dry tissue samples and the like which may contain infectious pathogens, and in particular to a laboratory dryer with powered airflow means and a hydrophilic filter material disposed on an exhaust outlet thereof.
2. Prior Art
Laboratory dryers for tissue samples and the like are known with powered airflow means. The Quick-Dry laboratory dryer marketed by Micro Diagnostics Corporation of Bethlehem, Pa. is an example. In order to improve the rate of drying of the samples as compared to simply leaving the samples exposed to the air, the device comprises at least one fan for establishing a powered flow of air over the samples and at least one heater disposed in the flow path. These elements are mounted in a housing where the samples can be placed in a semi-enclosed environment, protected from airborne dust. However, the exhaust air, i.e., the air that has already passed over the samples, moves directly out of the housing into the room in which the dryer is located.
Any water droplets, particles and the like which are extracted from the samples by the powered airflow become airborne. These droplets and/or particles are emitted by the dryer and can be ingested by laboratory personnel during respiration or by contact with surfaces on which the droplets or particles may settle. The separation of droplets and particles from the samples is driven substantially by the powering of the airflow. However, a powered airflow is desirable in order to speed drying. Therefore, there is an inherent danger to laboratory personnel in accelerated drying of samples which may be infected with bacteria or viruses using the ambient air of the room wherein the dryer is located.
Laboratory dryers may be used, for example, to dry samples on microscope slides, in petri dishes or on trays, or materials which are otherwise supported so as to be subject to air passing through the dryer. The specific material dried can be cultures prepared from tissue samples or actual pieces of biological tissue from a subject to be tested. It may be desirable to dry some of these samples at a higher temperature and others at a lower temperature, as necessary to avoid inducing changes to the samples which may affect the results of further tests to be conducted on the samples.
According to the present invention, a laboratory dryer is provided with a filter at a point downstream in the air flow of the samples, for example at the exhaust outlet of the drying apparatus. The filter includes a body of hydrophilic filter material, preferably of synthetic fibers such as polyethylene, whereby water droplets which may be extracted from the samples in the drying process are absorbed and held by the filter material. The filter material is preferably framed such that it can be readily removed, for example for autoclaving.
Biological filter apparatus are disclosed, for example, in U.S. Pat. Nos. 3,703,961-Feuer; 3,482,703-Roberts et al; 3,910,778- Shawgholi; 4,670,223 -Dalachapella; and 4,604,110-Frazier. According to the preferred embodiment of the present invention, the filter material is simply a layer of hydrophilic fibrous filter material disposed across the outlet of the dryer. The noted references, however disclose a number of rather complicated alternatives for filter elements which are believed effective for blocking the passage of biologically dangerous materials such as bacteria and viruses. The teachings of these patents are nevertheless incorporated herein, particularly as to filters useful for high performance filter applications as appropriate for drying especially dangerous pathogen containing samples.